Molarity

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Jonathan Marcial Dis 1K
Posts: 36
Joined: Fri Apr 06, 2018 11:03 am

Molarity

Postby Jonathan Marcial Dis 1K » Sun Apr 15, 2018 6:33 pm

How do we solve for molarity when we are given the amount of a solute in grams and then adding even more water? For example... "A solution is prepared by dissolving 55.1 g of KCl in approximately 75 mL of water and then adding water to a final volume of 125 mL. What is the molarity of KCl(aq) in this solution?" I don't understand how to get the final answer.

Alexander Hari 1L
Posts: 30
Joined: Wed Feb 14, 2018 3:02 am

Re: Molarity

Postby Alexander Hari 1L » Sun Apr 15, 2018 6:49 pm

I think in this problem, you need to convert the initial grams to moles and then multiply by the initial volume (75mL) and then set it equal to Mfinalx125mL since MinitialVinitial=MfinalVfinal, then solve for Mfinal

Chem_Mod
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Re: Molarity

Postby Chem_Mod » Sun Apr 15, 2018 6:52 pm

1. Find the concentration of KCl in the 75 mL solution
2. Set concentration you find in step 1 as M1. V1 = 75 mL. V2= Vfinal = (75 + 125 mL). Use the dilution formula to solve for the final concentration.

Jonathan Marcial Dis 1K
Posts: 36
Joined: Fri Apr 06, 2018 11:03 am

Re: Molarity

Postby Jonathan Marcial Dis 1K » Sun Apr 15, 2018 6:59 pm

Okay, this helps! Thank you!


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